Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.88	9.265%	$239.1592	$239.16	$239.15	$239.20
Purchase #2	$224.49	4.801%	$235.2678	$235.27	$235.25	$235.30
Purchase #3	$158.41	6.427%	$168.591	$168.59	$168.60	$168.60
Purchase #4	$35.39	4.432%	$36.9585	$36.96	$36.95	$37.00
Purchase #5	$193.66	12.858%	$218.5608	$218.56	$218.55	$218.60
Purchase #6	$57.67	3.639%	$59.7686	$59.77	$59.75	$59.80
Purchase #7	$80.50	6.488%	$85.7228	$85.72	$85.70	$85.70
7 purchase totals =	$969.00		$1,044.0287	$1,044.03	$1,043.95	$1,044.20